Apparatus for the automatic navigation of a sailing vessel

ABSTRACT

A navigation system for a sailing vessel which automatically sails the vessel from its present location to a destination location. The system responds to the prevailing wind conditions and characteristics of the craft to either sail directly or tack to the desired destination. Upon arrival at the destination location the system navigates the vessel to cause the vessel to keep a station in the immediate vicinity of the destination location.

Bond

[54] APPARATUS FOR THE AUTOMATIC NAVIGATION OF A SAILING VESSEL3,249,080 5/1966 McBrayer Inventor: Donald p c Bond, Princeton 3,312,4234/1967 Welch ..244/3.l8

j Primary Examiner-Andrew H. Farrell [73] Assignee: RCA CorporationAttorney-Edward J. Norton [22] Fllfid: Dec. 18, 1969 57 ABSTRACT [2 PP886,300 A navigation system for a sailing vessel which autov maticallysails thevessel from its present location to a destination location. Thesystem responds to the [52] us C 318/588 47 prevailing wind conditionsand characteristics of the craft to either sail directly or tack to thedesired [51] Int. Cl. ..B63h /00 destination Upon arrival at thedestination location [58] Fwd of serchwl 14/144 39; 318/588 the systemnavigates the vessel to cause the vessel to 318/581 5823 244/318 keep astation in the immediate vicinity of the destination location. I v [56]References Cited v 9 Claims,'4' Drawing Figures UNITED STATES PATENTS425,122 g/ s9o Cook; ..114/39 Y Z-ssa I0 55 i OTHER TELEMETRY SATELLTESENSORS TRANSMITTER COMPASS "$88" 27M l L 44 l r H i l 25 I l DOPPLER II m l SAIL I COUNT COMPUTER SERVO B I9 I i 24 p26 33 "GE Am l 5OEPHEMERIS RA L SAILING RECElVER l f COMPARATOR 7 BEARING 1 DECODERCOMPUTER COMPUTOR 54 3 I2 6 i 20 1 5 2| F 3| 32 1 A? 4' 48 7k 56IONOSPHERE I DEAD STORED CORRECTION l MEMO RECKON|NG- smum; g lfCOMPUTER 5 5 W 28 COMPUTER 46 PROGRAM I 61 l J L l DATA X COMMUNICATIONfi lEfi D|G|TAL COMPUTER 22 PROCESSOR I SENSOR 38 REMOTE com TRANSMITTER[4 1 Sept. 19, 1972 Pmmmssmwn 3.691.978

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WIND DIRECTION [)(XoJLo) I I I I N -M Ik +M S WIND S DIRECTION Flg.DIRECTION INVENTOR.

BY Donald 8. Bond gwqgmtz TORNEY PATENTEBSEPWHTZ 3.691.978

sum 3 or 3 RETURN COURSE I N VEN TOR.

Y Donald 5. Bond mun/J9 m1;

TTORNE Y APPARATUS FOR THE AUTOMATIC lJAVIGA'IION'OF A SAILING VESSELThis invention relates to the automatic navigation of a sailing vessel.

Automatic navigation systems are known in the prior art. Such systemsgenerally fall into two classes, i.e., the

.. remote. control type and the autopilot type. In both types theoperating procedure is to set or compute a range and bearing from thepresent location to a destination location and automatically move thecraft directly between the two points. Some of these prior art systemsalso provide compensation for the change in heading or attitude of thecraft in response to externally applied forces. Such forces may be thewind, ocean currents or even the change in weight of a rocket as fuel isconsumed.

Automatic navigation of sailing vessels is a complicated problem becausethe system must not merely compensate for prevailing wind and currentconditions, but in addition it must use the wind, either completely orpartially, as the motive force for the vessel.

When it is desired to tack a sailing vessel, that is to cause thevessels head to swing through the wind, the rudder and sail must beadjusted to point the craft across the wind. As the vessel heels beforethe wind while tacking, a proper balance must be maintained or the craftwill capsize. Furthermore, the craft must have a certain velocity in thewater as it completes the tack vacrossthe wind or it will not be able tomake a followup tack which will result in an in irons or stalledcondition before the wind. Another complication in the tacking maneuveris that the vessel will capsize if the rudder is moved too quickly whenturning into the wind.

ln general, when sailing from one point to another, the rudder must befirst positioned to head the craft on the desired bearing. Once thedesired bearing is attained, the rudder is aligned with the fore-aftaxis of the craft and the sail is positioned to catch the wind in amanner which will provide the greatest force vector in the direction ofthe desired bearing. Here, again, in bringing the craft about to thedesired bearing care must be taken never to head directly into the windor the craft will be stalled.

lnboth tacking and running free with the wind coming from the aftdirection, the sail must be periodically trimmed and in some instanceseven furled and unfurled.

As a result of the characteristics and problems inherent in sailing, theprior art does not disclose any practical automatic navigation systemfor a sailing vessel.

A very useful application for an automatic navigation system for asailing vessel is in the field of sea buoys. Moored, unattended buoyshave long been used at sea as navigation guides to mariners. Some buoyshave included sensors for measuring air and water characteristics.Practically all such buoys have been restricted to relatively shallowcoastal waters where the problems of anchoring the buoys are not severeand where the buoys are readily accessible for maintenance.

More recently, experimental buoys have been built for mooring inthe'deep ocean. Such deep-sea anchoring means are extremely expensive inboth initial installation cost and maintenance. The buoys themselvesmustbe very rugged to withstand strong wind and waves and the inducedmooring stresses. If the buoy is located at a great distance from ashore base, the cost of sending a sea-going buoy tender is excessive.

With one embodiment of the present invention a system of buoys may beset out on the ocean from a shore base and ultimately sailed to desiredlocations wherein they may be left unattended for the telemet'ering ofmeteorological and hydrological observations.

The automatic navigation system herein disclosed automatically sails avessel having a hull, a sail and a rudder to a given destination. Thestructure of the vessel determines a close haul angle of plus or minus Mwith respect to the wind direction (the plus and minus values may differif the vessel is asymmetrical about its fore-aft axis). Means areprovided for determining the present location of the vessel and therange and bearing from the present location to the destination. Thedirection of the windis determined and the bearing angle B from thepresent location to the destination with respect to the wind isdetermined. Means are provided for positioning the sail and the rudderof the vessel to sail directly to the destination when the absolutevalue of angle B is greater than the absolute value of angle M.Furthermore, means are provided for positioning the sail and the rudderof the vessel to sail to the destination on two or more tacks when theabsolute value of angle B is less than the absolute value of angle M.

In the drawings: I

FIG. 1 is a block diagram of an automatic navigation system according toone embodiment of the invention;

FIG. 2 is a chart illustrating the conditions under which a vessel maybe sailed from its present location directly to its destinationlocation;

FIG. 3 is a chart illustrating the conditions under which the vesselmust tack in order to sail from its present location to its destinationlocation; and

FIG. 4 is a chart showing the manner in which the vessel stationkeeps atthe destinationlocation.

The invention herein described may be practiced with a vessel having asail and a rudder, and is especially useful with a craft having a rigidor semi-rigid sail. Such a craft is disclosed in United States Pat.application Ser. No. 794,589, assigned to the same assignee as thepresent application. The craftin the referenced patent application isfurther characterized by a substantially circular hull structure which,in combination with the sail and rudder configuration allows the vesselto be oriented towards a desired location by setting the sail and rudderin predetermined positions. Utilization of the referenced craft permitsa simplification of the structure for practicing the present inventionin the preferred embodiment shown herein.

The substantially circular hull shown in the referenced application isnot essential for practicing the present invention. A conventional yatchhull may be used with the present invention but, for reasons set forthherein, a conventional yacht hull is less desirable.

Similarly, any wind energized propulsion means, such as an airfoil, acloth sail, or Flettner rotor may be substituted for the sail in thereferenced application. However, when a sail system of more complicatedhandling characteristics is used, several additional servomechanismcontrols will be required. The additional controls will requireadditional stored programs for operation thereof.

f ton,D.C.,U.S.A.

Other radio navigation systems, such as hyperbolic systems like OMEGA orLORAN may be substituted for the Transit system. Alternatively, pointlocation stations, such as sonar transmitters disposed at predeterminedpoints on the ocean bottom, may be employed for providing the desiredlocation information.

If four satellites are in appropriate polar orbits, one of them comesinto the view of any location on the surface of the earth every I or 2hours. During one satellite pass, it is possible to obtain a navigationfix at a terrestial location with a very small error.

In FIG. 1, a satellite passes within the radio line of sight of thepresent location of the sailing vessel and transmits appropriatenavigation and timing information. Antenna 11 located on the craftreceives the transmitted signals and provides the information toreceiver 12 via line 13. Receiver 12 provides the incoming signals todata processer 14 via lines l5, l6 and 17.

Line 15 is connected to the input terminal of Doppler count unit [8.Doppler count unit 18 determines the total number of cycles of theheterodyned Doppler signal during a selected time interval.

Line 16 is connected to the input terminal of an ephemeris decoder 19which translates the digital code representing the up-to-date geometricelements of the satellite orbit into computer language.

Line 17 is connected to the input terminal of an ionosphere correctioncomputer 20. lonosphere correction computer 20 provides a correction tothe Doppler count via line 21. The correction for ionospheric conditionsis based upon the comparision of signals at two received frequencies.Output signals from the data processor 14 are provided at the inputterminals to a general purpose digital computer 22 via lines 23 and 24.

Lines 23 and 24 carry navigation fix information to a section of thegeneral purpose digital computer 22 termed the latitude-longitude (My)computer 25. Latitude-longitude computer 25 determines the presentposition of the vessel and encodes the resulting coordinates andprovides corresponding signals on lines 26 and 27.

The latitude and longitude coordinates of the desired location (A 1.1.are stored in the computer memory 28. Access to the computer memory 28may be had locally or via a remote command transmitter 29 linked to thememory by way of the communications link 30. Link 30 may comprise aradio receiver cooperating with transmitter 29. The stored coordinatesof the desired location are represented by a signal coupled from thememory via line 31.

The signals representing the present location of the vessel on line 26and the signals representing the desired destination location on line 31are compared in the comparator 32. Comparator 32 provides signalscorresponding to the difference between the coordinates of the presentlocation and the coordinates of the desired location on line 33.

The signals on line 33 are provided to a range and bearing computer 34.Range and bearing computer 34 performs a trigonometric transformation togive the range and hearing from the present position to the desiredposition. In suitable linear units, the range R is given by R= (AA)+(Ap.)

where AA A A) M u u,- The bearing (relative to true north) is given byA,

where A tan AA/Ap.

The reference direction for the range and bearing computer 34 isprovided by the magnetic compass 35. The corresponding signal isprovided to the range and bearing computer 34 from the compass 35 vialine 36.

When the navigation data source is intermittent, as is the case where anorbiting satellite is the data source, means must be provided togenerate the range and bearing continuously between the times of fixes.This function is performed by dead reckoning computer 37, whichcontinuously computes the range and bearing to the destination.

The dead reckoning computer 37 obtains information as to the speed ofthe craft through the water by the commonly used technique of a taffraillog water current sensor 38. Sensor 38 comprises a propellor andelectrical generator whose speed varies linearly with v, the speed ofthe craft through the water and which measures by counting totalrevolutions, the distance traveled through the water during a timeinterval 1 1,. The corresponding signal from sensor 38 is coupled to thedead reckoning computer 37 via line 39. Water current sensor 38 alsoincludes a vane for sensing the direction of movement of the water withrespect to the fore-aft axis of the craft.

Computer 37 together with sensor 38 perfonns the integration r d=f 2 wita 7VA tl and also resolves d into north and east components of distancetravelled with respect to the water:

d,,=dcosA d =dsinA proximate position of the craft between navigationfixes is computed.

The continuously generated signals corresponding. to the range andbearing to the destination 'are coupled to the sailing computer via line42, In addition, a signal corresponding to the wind direction,generated. in the wind'direction sensor 43, isprovided at an inputterminal'of the sailing computer 41 via line Wind direction sensor 43 isprovided. with a reference direction signal from compass35 vialine 45.

Depending upon the prevailingwind conditions and the bearing to thenewlocation, appropriate sailing maneuvers for the most efficientsailing of the vessel are called up'from the storedsailing program 46.The stored sailingpro'gram is enteredvialine 47 and-theappropriatesignals corresponding to the desired maneuversare-coupled'to-the sailing computer'41 via line 48..

The stored sailing program 46 is a look-up table wherein the appropriatepositions of the sail-and the rudder with respect to an arbitrarilydeterminedforeaft axis of the'craft are'contained. The look-up table isempirically determined'for the particular craft.

The appropriate positions of the sail and rudder for the most efficientsailing of the craft are initially experimentally determined and enteredin the look-uptable.

Specifically, the preferred craft previously mentioned has, by virtue ofits construction, the ability to traverse the distance between thepresent location of the craft and another location by a single settingof the sail and a single setting of the rudder in predeterminedpositions with respect to the arbitrary fore-aft axis through thesubstantially circular hull. This particular craft can head into thewind without being stalled even though no headway can be made in asector defined by the close-haul angle of the craft and centered aboutthe direction of the wind. The sail on the preferred circular hull craftcan be turned clockwise or counter-clockwise with respect to the winddirection without detrimental effects. Furthermore, the sequence ofsetting the sail and the rudder and the rate of movement of both hasbeen found to be immaterial for this particular craft.

Therefore, for each angle, B, the sailing program 46 provides signals tothe sailing computer 41 corresponding to an experimentally determinedsail position and rudder position.

Sailing computer 41 provides corresponding signals to. the sail servosystem 49 via line 50. Sail servo 49 controls the orientation of thesail 52 via the mechanical link 51. Simultaneously, the sailing computer41 provides corresponding signals to the rudder servo system 53 via line54. Rudder servo 53 orients the rudder servo system 53 via line 54.Rudder servo 53 orients the rudder 55 via the mechanical link 56.

All of the functions described by the blocks contained within thedigital computer 22 are internally performed in computer 22. There aremany general purpose digital computers readily available for performingthe functions of digital computer 22. One such computer is the PDP-8computer built by the Digital Equipment Corporation, of Maynard, Mass.The programmlng of such a digital computer to perform the stepspreviously described is well known in the prograinming art.

Sailing craft are characterized, as a result of their individualstructure, by what is termed as a close-haul angle. The close-haul angleof a sailing vessel is defined as the closest angle to the directionfrom which the wind blows which will allow the vessel to gain distancetoward the windward direction. A sailing vessel is unable to saildirectly into the wind, and the close-haul angleof plus or minus M withrespect to the direction from which the wind blows (the'plus and minusvalues may differv if the vessel'is asymmetrical about its-foreaft axis)defines a sector within whichthe vessel may not saildirectly to anypoint contained within'the sector.

When asailing craft does .in fact head into-the sector defined by theangles plus and-minus M at: low speed the craft will come to a stop,heading into the wind, and is said to be stalled or in irons." When acraft is in irons it cannot turn port or starboard but will drift slowlydownwind. The vessel will be able to get out of irons only withdifficulty and with the application of some external force or change inthe prevailing wind conditions. A When it is desired to sail a craftto-a location within the sector defined by the close-haul angle thecraft must tack in order to reach that location. One or more tacks maybe necessary depending upon the range and prevailing wind conditions.

Referring now to FIG. 2, together with FIG. 1, the vessel is launchedfrom a land base at point L. At some time thereafter, satellite 10appears above the horizon at the location of the vessel and the onboardequipment computes thepresent coordinates (Mu) of the point P. Thedestination coordinates (M, p. of the point D are stored in the memory28. The wind direction is at the angle C with respect to north. Sailingcomputer 41 determines that the bearing B (with respect to the winddirection) to the destination is greater than the closehaul angle M.Stored sailing program 46 calls up the appropriate sailing maneuvers,that is, the sail position and the rudder position to sail directly frompoint P to point D at a bearing of A with respect to north and a rangeR. With the sail 52 and the rudder 55 positioned in accordance with thecommands from the sailing computer 41, the vessel starts to sail acourse directly to point D.

As the vessel sails the dead reckoning computer 37 continuously computesthe approximate location of the vessel by resolving the components (1,,and d shown in FIG. 2.

Returning to FIG. 1, a telemetry transmitter 57 is provided to transmitthe continuously generated signals corresponding to range and bearingfrom computer 34 on line 58.

A suitable antenna 59 is coupled to the telemetry transmitter 57 forthis purpose. The signals on line 27 corresponding to the accuratelydetermined present position are also provided at transmitter 57 in orderto relay this information to a remote monitoring station. In addition,signals corresponding to the parameters determined by other sensors suchas sensors 43 and 38 are provided at transmitter 57 via line 60 forrelay to the-monitoring station.

Referring now to FIG. 3, together with FIG. 1, satellite 10 passeswithin the radio line of sight of the vessel and the present coordinates()up.) of the point P are determined. The coordinates (A of thedestination D under these particular conditions lie within the sectordetermined by the close-haul angle of plus and minus M. The vesseltherefore cannot traverse the range R on a bearing of A with respect tonorth under these prevailing wind conditions. Therefore, the storedsailing program 46 will provide the necessary sail and rudder positioninformation to enable the vessel to tack to the destination location D.

The sailing computer 41 determines the existence of the conditionsrequiring tacking by comparing the original bearing A with respect tonorth, provided by the range and bearing computer 41, with the presentwind direction provided by sensor 43. When tacking is required, sailingcomputer 41 computes an offset to the original bearing A to determine anew bearing A,. Sailing computer 41 also computes a new range R, whichis arbitrarily programmed to be approximately 0.7 of the original rangeR in the case where it has been decided to sail to the destination D intwo tacks.-

The new bearing A 1 is translated into bearing B with respect to thewind in computer 41. Bearing B and 1 range R are provided to the storedsailing program 46 via line 47 and the sail 52 and rudder 55 arepositioned according to the look-up table.

The vessel will sail on the first tack until the distance R has beentraversed or until the satellite 10 passes over, whichever comes first.

If the satellite 10 passes over before the first tack is completed a newrange and bearing will be set for point D based on the updatedinformation.

If the distance R, is traversed before the satellite 10 passes over thesystem will compute the new bearing B and range R when the vesselarrives at point P, The vessel arrives at point P when the continuouslygenerated range information from the dead reckoning computer 37 matchesthe computed range R in the sailing computer 41.

At point P, the system determined the range R and bearing B, withrespect to the wind and if the bearing B is now beyond the close haulsector the craft will sail directly to the destination point D. If thecraft is within the close haul sector at point P the system will againinitiate the procedures to sail from point P to point D on two tacks.Changing wind conditions may cause the bearing B at point D to fallwithin the close haul sector.

Once having arrived at the destination point D, it is desired tomaintain or station-keep the vessel in the immediate vicinity of point Din order to perform its meteorological and hydrological functions.

Referring to FIG. 4, a preferred method of stationkeeping is shown.Assume the craft is at station at time t==0, the time of the initialnavigation fix. In an x, y cordinate system the selected station is atx=0, y=0. The wind vector is along the y-axis and is directed toward thenegative direction. Navigation fixes are made at equal time intervalsAg, starting at t=0.

Starting at point 0,0 the vessel is sailed at 90 with respect to thewind vector for a time At/Z. Course reversals at times of I=At, 2At, aremade until the next satellite passes over and a navigation fix isobtained at =t,.

If ocean currents are not appreciable the craft will sail back and forthbetween the points A and B in FIG. 4.

'At the time of the navigation fix, t=t;, a retrace course back to thestation at 0, 0 is determined by the system. FIG. 4 illustrates theretrace courses when currents or other perturbing forces cause thevessel to drift. If the bearing from the craft location, at time t, tothe point 0,0 lies outside of the close-haul angle sector, then thecraft will return on a direct path to its desired station. However, ifthe bearing of the return course lies within the close-haul sector thenthe craft will tack to its desired station as shown in FIG. 4. Point Pin FIG. 4 is determined by the continuously generated information fromthe dead reckoning computer 37. In this manner, the sailing craft willbe kept within a few tenths of 21 nautical mile from the desired stationdespite any drift caused by water currents.

Point C in FIG. 4 is also determined approximately by the dead reckoningcomputer 37. However the position so determined will differ from themore precise fix from the radio navigation system. The difference inposition or closing error" provides a measure of the magnitude anddirection of the prevailing ocean sur-' face current. The system of thepresent invention thus serves as a sensor of ocean current.

With the wind and ocean currents in a more favorable orientation withrespect to the vessel, the craft will sail between points A and B inFIG. 4 and remain extremely close to the desired station at 0,0.

What is claimed is:

1. An automatic navigation system for sailing a vessel to a givendestination, said vessel having a hull, a sail, and a rudder, thestructure of said vessel determining a close haul angle of plus or minusM with respect to the wind direction, said system comprising:

means for generating a first set of signal waves corresponding to thepresent location of said vessel;

means for generating a second set of signal waves corresponding to saiddestination;

a signal wave comparator for comparing said first set of signal wavesand said second set of signal waves and for providing a signal wavecorresponding to the bearing from the present location to saiddestination;

means for generating signal waves corresponding to the wind direction;

signal processing means responsive to said signal waves corresponding tothe wind direction and to said signal wave corresponding to the bearingfrom the present location to the destination for providing a signal wavecorresponding to the angle B of the bearing from said present locationto said destination with respect to said wind direction;

a sail servomechanism including a sail positioning device coupled tosaid sail, said sail servomechanism being responsive to said signalprocessing means; and

a rudder servomechanism including a rudder positioning device coupled tosaid rudder, said rudder servomechanism being responsive to said signalprocessing means;

said sail servomechanism and said rudder servomechanism positioning saidsail and said rudder to sail said vessel directly to said destinationfrom said present location when the value of said angle B is greaterthan the value of said angle M, and said sail and said rudder beingpositioned by said sail and rudder servomechanism to sail said vessel ontwo or more tacks to said destination from said present location whenthe value of said angle B is less than the value of said angle M.

2. The system according to claim 1 wherein the sail of said vesselcomprises a rigid or semi-rigid airfoil structure.

3. The system according to claim 1 wherein the hull of said vesselcomprises a substantially circular structure.

4. The system according to claim 1, further comprising means responsiveto said first and second set of signal waves for providing a signal wavecorresponding to the range between the present location and saiddestination.

5. The system according to claim 1, wherein the means for generatingsaid first set of signal waves includes navigation information signalwaves from at least one earth orbiting satellite.

6. An automatic navigation system for sailing a vessel to a givendestination, said vessel having a hull, a sail and a rudder, thestructure of said vessel determining a close haul angle of plus or minusM with respect to the wind direction, the system comprising:

means including at least one earth orbiting satellite 9 for periodicallygenerating a first set of signal waves corresponding to the presentlocation of said vessel;

means for generating a second set of signal waves corresponding to saiddestination;

means responsive to said first and second set of signal waves forperiodically providing a third and fourth set of signal wavescorresponding respectively to the bearing and range from said presentlocation to said destination;

means for generating a signal wave corresponding to the wind direction;

signal processing means responsive to said signal wave corresponding tothe wind direction and to said third set of signals for periodicallyproviding a fifth set of signal waves corresponding to the angle B ofthe bearing from said present location to said destination with respectto the wind direction;

a sail servomechanism including a sail positioning device coupled tosaid sail, said sail servomechanism being responsive to said fourth andfifth set of signal waves; and

a rudder servomechanism including a rudder positioning device, coupledto said rudder, said rudder servomechanism being responsive to saidfourth and fifth set of signal waves;

said sail servomechanism and said rudder servomechanism positioning saidsail'and said rudder to sail said vessel directly to said destinationfrom said present location when the value of said angle B is greaterthan the value of said angle M, said sail and said rudder beingpositioned by said sail and rudder servomechanisms to sail said vesselon two or more tacks to said destination when the value of said angle Bis less than the value of said angle M, and said sail and rudderservomechanisms positioning said sail and rudder to maintain theposition of said vessel in the vicinity of said destination.

7. The system according to claim 6, wherein the sail of said vesselcomprises a rigid or semi-rigid airfoil structure.

8. The system according to claim 6, wherein the hull of said vesselcomprises a substantially circular structure.

9. The system according to claim 6, wherein said means for periodicallydetermining the present location of said vessel comprises:

a source of radio frequency signal waves, located on said at least onesatellite for periodically providing a plurality of reference signalwaves, said reference signal waves being encoded with navigationinformation; a receiver, located on said vessel, for receiving saidreference signal waves; data processing means, coupled to said receiver,for extracting said navigation information from said plurality ofreference signal waves and for providing a corresponding plurality ofnavigation information signal waves; and means responsive to saidplurality of navigation information signal waves for periodicallycomputing the coordinates of the present location of said vessel and forproviding said first set of signal waves.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 691,978 Dated September 19, 1972 Invent0 Donald Spencer Bond It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 6, line 29 (1 I)" should be (l u Column 7, line 58 i "1 At"should be T Ail-- Column 7, line .60 "at t should be -at t t Signed andsealed this 10th day of April 1973 (SEAL) Attest:

EDWARD M.FLETCHER',JR. ROBERT G OTTSCHALK I Attestlng OfficerCommissioner of Patents FORM PO-IOSO (10-69] USCOMM-DC 60376-P69 3530672 u.5. GOVERNMENT pnnmuc. OFFICE 1 was o-ase-sa:

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No. 3,691,978 Dated September 19, 1972 Inventofls) Donald Spencer Bond It iscertified that ertor appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Signed and sealed this 10th day of April 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR.

ROBERT G'OTTSCHALK Y Attesting Officer Commissioner of Patents FORMPO-IOSO (10-69) USCOMM-DC 60376-P69 3530 6'72 9 u.s. GOVERNMENT PRINTINGornc: 1 I969 o-zee-saa Column 6, line 29 (1 u)" should be (A p Column 7,line 58 "I At" should be -T ='At-- Column 7, line 60 "'at ,t, fihouldvbe at t t

1. An automatic navigation system for sailing a vessel to a givendestination, said vessel having a hull, a sail, and a rudder, thestructure of said vessel determining a close haul angle of plus or minusM with respect to the wind direction, said system comprising: means forgenerating a first set of signal waves corresponding to the presentlocation of said vessel; means for generating a second set of signalwaves corresponding to said destination; a signal wave comparator forcomparing said first set of signal waves and said second set of signalwaves and for providing a signal wave corresponding to the bearing fromthe present location to said destination; means for generating signalwaves corresponding to the wind direction; signal processing meansresponsive to said signal waves corresponding to the wind direction andto said signal wave corresponding to the bearing from the presentlocation to the destination for providing a signal wave corresponding tothe angle B of the bearing from said present location to saiddestination with respect to said wind direction; a sail servomechanismincluding a sail positioning device coupled to said sail, said sailservomechanism being responsive to said signal processing means; and arudder servomechanism including a rudder positioning device coupled tosaid rudder, said rudder servomechanism being responsive to said signalprocessing means; said sail servomechanism and said rudderservomechanism positioning said sail and said rudder to sail said vesseldirectly to said destination from said present location when the valueof said angle B is greater than the value of said angle M, and said sailand said rudder being positioned by said sail and rudder servomechanismto sail said vessel on two or more tacks to said destination from saidpresent location when the value of said angle B is less than the valueof said angle M.
 2. The system according to claim 1 wherein the sail ofsaid vessel comprises a rigid or semi-rigid airfoil structure.
 3. Thesystem according to claim 1 wherein the hull of said vessel comprises asubstantially circular structure.
 4. The system according to claim 1,further comprising means responsive to said first and second set ofsignal waves for providing a signal wave coRresponding to the rangebetween the present location and said destination.
 5. The systemaccording to claim 1, wherein the means for generating said first set ofsignal waves includes navigation information signal waves from at leastone earth orbiting satellite.
 6. An automatic navigation system forsailing a vessel to a given destination, said vessel having a hull, asail and a rudder, the structure of said vessel determining a close haulangle of plus or minus M with respect to the wind direction, the systemcomprising: means including at least one earth orbiting satellite forperiodically generating a first set of signal waves corresponding to thepresent location of said vessel; means for generating a second set ofsignal waves corresponding to said destination; means responsive to saidfirst and second set of signal waves for periodically providing a thirdand fourth set of signal waves corresponding respectively to the bearingand range from said present location to said destination; means forgenerating a signal wave corresponding to the wind direction; signalprocessing means responsive to said signal wave corresponding to thewind direction and to said third set of signals for periodicallyproviding a fifth set of signal waves corresponding to the angle B ofthe bearing from said present location to said destination with respectto the wind direction; a sail servomechanism including a sailpositioning device coupled to said sail, said sail servomechanism beingresponsive to said fourth and fifth set of signal waves; and a rudderservomechanism including a rudder positioning device, coupled to saidrudder, said rudder servomechanism being responsive to said fourth andfifth set of signal waves; said sail servomechanism and said rudderservomechanism positioning said sail and said rudder to sail said vesseldirectly to said destination from said present location when the valueof said angle B is greater than the value of said angle M, said sail andsaid rudder being positioned by said sail and rudder servomechanisms tosail said vessel on two or more tacks to said destination when the valueof said angle B is less than the value of said angle M, and said sailand rudder servomechanisms positioning said sail and rudder to maintainthe position of said vessel in the vicinity of said destination.
 7. Thesystem according to claim 6, wherein the sail of said vessel comprises arigid or semi-rigid airfoil structure.
 8. The system according to claim6, wherein the hull of said vessel comprises a substantially circularstructure.
 9. The system according to claim 6, wherein said means forperiodically determining the present location of said vessel comprises:a source of radio frequency signal waves, located on said at least onesatellite for periodically providing a plurality of reference signalwaves, said reference signal waves being encoded with navigationinformation; a receiver, located on said vessel, for receiving saidreference signal waves; data processing means, coupled to said receiver,for extracting said navigation information from said plurality ofreference signal waves and for providing a corresponding plurality ofnavigation information signal waves; and means responsive to saidplurality of navigation information signal waves for periodicallycomputing the coordinates of the present location of said vessel and forproviding said first set of signal waves.